The following methods have been known for obtaining an ester compound by reacting a fluorine-containing alcohol represented by the following general formula (A):F(CF2CF2)nCH2CH2OH  (A)(wherein n is an integer of 1 to 10) and having a chemical structure in which a perfluoroalkyl group having even-numbered carbon atoms is bonded to the β-carbon atom of ethyl alcohol [this structure corresponds to a compound of the general formula (1) described in this Description wherein k is 2 and m is 0], with (meth)acrylic acid.
A method of subjecting the fluorine-containing alcohol and (meth)acrylic acid to dehydration in the presence of an acid catalyst (Patent Literatures 1 to 4 shown below).
A method of subjecting the fluorine-containing alcohol and a (meth)acrylic acid ester to ester interchange in the presence of an acid catalyst (Patent Literatures 1 to 3 shown below).
A method of subjecting the fluorine-containing alcohol and (meth)acrylic acid chloride to dehydrochlorination (Patent Literatures 1 to 3 shown below).
Also, there is known a method of reacting the fluorine-containing alcohol and methacrylic acid anhydride in the presence of dimethylaminopyridine (a catalyst) (Non-Patent Literature 1 shown below).
Meanwhile, there is known a method of converting, into a (meth)acrylic acid ester, a fluorine-containing alcohol having a particular chemical structure different from the chemical structure of the above-mentioned fluorine-containing alcohol (A) and represented by the following general formula (B):CnF2n+1CH2OH  (B)(wherein n is an integer of 3 to 9 in Patent Literature 5 shown below and an integer of 2 to 20 in Patent Literature 6 shown below) [the particular chemical structure corresponds to a compound of the general formula (1) described in this Description wherein k is 1 and m is 0] (Patent Literatures 5 and 6 shown below).
In the Patent Literature 5, it is described that, in subjecting the fluorine-containing alcohol of the general formula (B) and (meth)acrylic acid to dehydration to produce their ester, no reaction proceeds even when the above-mentioned acid catalyst is used. That is, since fluorine atom exhibits its characteristic property, it is difficult to predict whether or not esterification proceeds in the esterification of a fluorine-containing alcohol containing a large number of fluorine atoms.
Incidentally, in the Patent Literature 5, the fluorine-containing alcohol represented by the general formula (B) is reacted with acrylic acid chloride in the presence of barium chloride to obtain a (meth)acrylic acid ester. Also, in the Patent Literature 6, the fluorine-containing alcohol represented by the general formula (B) is reacted with (meth)acrylic acid anhydride in the presence of an acid catalyst.
In literatures other than shown above, there are disclosed various techniques (Patent Literatures 7 to 17) of using fluorine-containing alcohols of different structures to obtain corresponding (meth)acrylic acid esters. However, as mentioned previously, since fluorine atom has its characteristic property, it has been difficult to predict whether or not the esterification of such a fluorine-containing alcohol proceeds smoothly.
(Meth)acrylic acid chloride, which is widely used in these conventional techniques, is an esterification agent of high reactivity. However, having high reactivity, this esterification agent is unstable and difficult to handle, and has a drawback of forming a dimer with the passage of time (Patent Literature 18).
The method of subjecting a fluorine-containing alcohol and (meth)acrylic acid to dehydration using an acid catalyst, to obtain an ester, uses inexpensive raw materials and is economical and accordingly is employed widely. However, when the dehydration using an acid catalyst is applied in conversion of the fluorine-containing alcohol having a chemical structure represented by the general formula (A), into its (meth)acrylic acid ester, it was found drawbacks that (meth)acrylic acid is required in excess and that there is formed, besides the intended ester compound, a considerable amount of an impurity represented by the following general formula (C):F(CF2CF2)nCH2CH2OCOCHRCH2OCH2CH2(CF2CF2)nF  (C)(wherein R is a hydrogen atom or a methyl group; and n is an integer of 1 to 10). This impurity is considered to be formed by addition of the fluorine-containing alcohol to the double bond of the produced (meth)acrylic acid ester.
Similarly, there is widely employed the method of using a lower alkyl (meth)acrylate [e.g. methyl (meth)acrylate] and conducting ester interchange in the presence of an acid catalyst, because the method uses inexpensive raw materials and is economical. However, it was found drawbacks that, when the above ester interchange is conducted using a particular, fluorine-containing alcohol represented by the general formula (A), a considerable amount of an impurity represented by the general formula (C) is formed similarly to the above case.
Further, it was found drawbacks that, when esterification of fluorine-containing alcohol is conducted using (meth)acrylic acid anhydride in the presence of an acid catalyst described in the Patent Literatures 6 to 10, the above-mentioned addition product [general formula (C)] is formed (in the Patent Literatures 7 to 10, the by-produced trifluoroacetic acid is a strong acid of pKa=0.5).
There is no formation of the above-mentioned addition product when, as in the Non-Patent Literature 1, a fluorine-containing alcohol and methacrylic acid anhydride are reacted under a basic condition. However, it is necessary to produce or procure (meth)acrylic acid anhydride. Acrylic anhydride, in particular, has a strong tearing property; therefore, in its production or handling, there is required a facility in which consideration has been made for the above problem. Therefore, such a method is unsuitable as a method for industrial production.
Meanwhile, it is known that the fluorine-containing alcohol represented by the general formula (A) reacts with a sulfonic acid halide in the presence of a tertiary amine to form its sulfonic acid ester (Non-Patent Literature 2). It is also known that this sulfonic acid ester releases a sulfonic acid salt under a basic condition to give an olefin (Non-Patent Literature 3).
As described above, production of fluorine-containing alkyl (meth)acrylate employs a highly characteristic reaction and, therefore, it is quite unpredictable whether or not the reaction proceeds smoothly.
Non-Patent Literature 1 Kruper, Maarten J.; Moeller Martin; J. Fluorine Chem., 1997, 82(2), 119-124.
Non-Patent Literature 2 Elshani, Sadik; Kobzar, Evgeny; Bartsh, Richard A.; Tetrahedron 2000, 56(21), 3291-3302
Non-Patent Literature 3 Germain, A.; Commeyras, A.; Tetrahedron 1981, 37, 487-492
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